GB2291150A

GB2291150A - Disc brake

Info

Publication number: GB2291150A
Application number: GB9513244A
Authority: GB
Inventors: Richard Arnold Bass; Stephen Bryan
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1994-07-08
Filing date: 1995-06-29
Publication date: 1996-01-17
Anticipated expiration: 2015-06-29
Also published as: GB9513244D0; GB2291150B

Abstract

A disc brake caliper comprises at least one brake pad 11 movable on a caliper body 10 axially of brake disc 12, the body including a pair of circumferentially spaced abutments 16, 17 which support the pad against circumferential displacement relative to the caliper body under braking. The abutment 17 is provided by a pad contacting member 29 supported on rollers 26 for movement towards the disc during brake application. Springs 37 positioned between flange 31 and a surface 22a return the member 29 to its start position on cessation of each brake application. As described, there are two brake pads 11 each being urged towards a respective side of the disc by three different diameter pistons 13. In an alternative embodiment, a brake pad (60, figure 8) abuts a contacting member (64) which moves on rollers (63) in a plane inclined at an angle to the disc axis. <IMAGE>

Description

DISC BRAKE CALIPERS This invention relates to disc brake calipers in which one or more disc brake pads are supported for movement towards and away from an associated brake disc in a caliper body.

Such calipers used in high performance vehicles such as racing cars suffer from problems due to the high braking forces experienced causing high frictional resistance between the supporting abutments and the pads which acts in opposition to any brake application force and thus reduces braking torque.

It is an object of the present invention to provide a caliper construction which at least mitigates the above problem.

Thus, according to the present invention, there is provided a disc brake caliper comprising a caliper body supporting at least one disc pad for movement towards and away from an associated brake disc between a pair of circumferentially spaced abutments which support the pad against circumferential displacement relative to the caliper body under braking, at least one of said pair of abutments comprising a plurality of rollers, a pad contacting member which overlies and is supported on the rollers for movement from a start position towards the disc during application of the brake, and resilient means for returning the pad contacting member to its start position on cessation of each brake application.

Preferably the pad contacting member and rollers comprise a subassembly which is detachably secured to the remainder of the caliper body.

This sub-assembly may include a support member on which the rollers are mounted and to which the pad contacting member is also secured.

Said at least one abutment may be formed at an angle to the associated brake disc so that as the pad is moved towards the disc the pad is also displaced circumferentially to a limited extent in the same direction of the normal forward direction of rotation of the associated disc.

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig 1 is a perspective underside view of part of a disc brake caliper in accordance with the present invention with one brake pad removed; Fig 2 is an underplan view of part of the right hand half of the caliper of Fig 1 taken in the direction of arrow A of Fig 1; Fig 3 is a view in the direction B of Figure 1 showing details of a trailing end pad supporting abutment in accordance with the present invention; Fig 4 is an end view in the direction C of Figure 3; Fig 5 is a section on line D-D of Figure 4; Fig 6 is a scrap perspective view of a leading end pad supporting abutment used in the brake of Figs. 1 and 2;; Fig 7 is an exploded perspective view of the pad supporting abutment of figures 3 to 5, and Fig 8 is a diagrammatic view of a caliper provided with an angled pad supporting abutment used in combination with needle roller support.

Referring to figures 1 and 2 these show part of a disc brake caliper comprising a body 10 which supports two disc brake pads 11 (only one of which is shown in the drawings for clarity) for movement towards and away from an associated brake disc 12 (see figure 2) under the action of six hydraulically operated pistons 13. As can be seen from figure 2, pistons 13 are of different diameter. The two pistons 13a which actuate the leading end of each pad 11 (ie that portion which first makes contact with the rotating brake surface of the disc) are of the smallest diameter in order to counteract the tendency of the leading end of the pad to dig in and hence produce tapering pad wear.

The pads 11 each comprise a friction material layer 14 and a backing plate 15. The pads may have a traditional metal backing pad 15 onto which the friction material layer 14 (eg sintered material) is bonded. Alternatively, the backing pad and friction material layer may be a carbon/carbon composite or any other suitable configuration.

The brake pads 11 have their backing pads 15 guided between pairs of abutments 16, 17 associated with the leading and trailing ends of each brake pad respectively.

The pad abutments 16 at the leading ends of the pads are of the form shown in greater detail in figure 6 and consist basically of a low conductivity generally L-shaped contacting member 18 which is held in position on a stepped portion 19 of the disc brake body by a retaining plate 20 which is secured in position by allen bolts 21. Each of the abutments 16 associated with the leading ends of each pad is of the general form described above and shown in figure 6.

Turning now to the subject of the present invention, the abutments 17 associated with the trailing end of each pad comprise a generally T-shaped support member 22 which is secured to a stepped portion 23 of the caliper body by a pair of allen bolts 24 which extend through one end of the cross piece 22' of the support member 22.

A needle roller assembly 25 is supported on a planar portion 22" of support member 22. The needle roller assembly comprises needle rollers 26 held captive in cage member 27 by local deformation 28 of the cage member. A pad contacting member 29 overlies and is supported by the needle roller assembly 25.

The contacting member is provided with two end flanges 30 and 31 and a base flange 32 and is located on the support member 22 by a pin 33 having a head 34. The pin extends through holes 35 in the end flanges 30 and 31 and a bore 36 in the support member 22. Trapped between the end 22a of support member 22 and the end flange 31 is a pair of corrugated leaf spring members 37 which are located in the back to back configuration and also include holes 38 through which pin 33 extends.

As will be appreciated each abutment 17 is thus a self-contained sub-assembly which can be removed from the caliper body in one piece.

The caliper of the present invention operates as follows.

When the pads 11 are brought into contact with the disc 12 by the hydraulic pistons 13, in the normal manner, the trailing ends of the backing plates 15 contact their associated abutments 17 as a result of the movement of the braking portion of the disc in direction Y of figures 1, 2 and 7. The movement of the pads towards the disc is in direction X of figures 1, 2 and 7 and the contacting members 29 move relative to the support members 22 against the action of leaf springs 37 which become squashed flat between flange 31 and the end 22a of support member 22 . To allow this movement of the contacting members 29 the internal dimension c of each contacting member exceeds the corresponding dimension s of each supporting member by the necessary amount.

As will be appreciated this movement of the contacting members 29 is facilitated by the rollers 26 which support each contacting member 29 on its associated support member 22.

When the disc brake is released the hydraulic pistons 13 retract sufficiently to allow the pads 11 to cease generating any braking effect and thus the backing plates 15 no longer apply a large force to the associated contacting members 29 thus allowing the contacting members to retract away from the associated brake disc under the action of leaf springs 37. Thus during each brake application the contacting members 29 slide on rollers 26 towards the brake disc with the associated pad backing plates 15 and the contacting members to retract away from the associated disc brake under the action of leaf springs 37. Thus during each brake application the contacting members 29 slide on rollers 26 towards the brake disc with the associated pad backing plates 15 and the contacting members are slid back to their initial starting position on the cessation of each brake application under the action of leaf springs 37 which are capable of moving the contacting members 29 over the rollers 26 when no braking effect is being generated.

Figure 8 shows part of an arrangement in which pad backing plate 60 is supported from a disc brake caliper body 61 via rollers 62 which operate on a support member 63 which is inclined to the brake disc at an angle e. By angling the rollers 62 and support member 63 at angle e it is again possible to significantly reduce the tendency of the associated pad to jam in the caliper body when the brake is applied. Typically angle e is up to 13 degrees.

Between the backing plate 60 and the rollers 62 is disposed an angled contacting member 64 which moves in direction X as the brake pads are applied against the disc 65 by pistons 66. The use of this angled contacting member 64 enables the ends 60a of the backing plate 60 to be right-angled and not inclined which simplifies manufacture.

As will be appreciated the rollers 62, support member 63 and angled contacting member 64 can all conveniently be formed as a self-contained sub-assembly in a similar manner to abutment 17 described in detail above.

As described above in relation to figures 1 to 7 the leading end pistons 13a are the smallest in diameter in order to counteract the tendency of the leading end of each pad to dig in and hence produce tapering pad wear. Since this tendency for greater braking effect at the leading end of each pad is due, at least in part, to the inter pad/abutment friction which take place at the trailing end of each pad, it will be appreciated that using the abutment arrangements of the present invention it should be possible to reduce, if not eliminate, the piston diameter differential between the leading and trailing end of each pad.

The present invention thus provides a number of alternative constructions which reduce the problem of inter pad/abutment friction and hence produce higher braking torque.

Claims

1. A disc brake caliper comprising a caliper body supporting at least one disc brake pad for movement towards and away from an associated brake disc between a pair of circumferentially spaced abutments which support the pad against circumferential displacement relative to the caliper body under braking, at least one of said pair of abutments comprising a plurality of rollers, a pad contacting member which overlies and is supported on the rollers for movement from a start position towards the disc during application of the brake, and resilient means for returning the pad contacting member to its start position on cessation of each brake application.

2. A caliper according to Claim 1 in which the pad contacting member and rollers form a sub-assembly which is detachably secured to the remainder of the caliper body.

3. A caliper according to Claim 2 in which the sub-assembly comprises a support member which is secured to the remainder of the caliper body and on which the rollers are mounted, the pad contacting member also being secured to the support member.

4. A caliper according to Claim 3 in which the resilient means acts between the pad contacting member and the support member.

5. A caliper according to Claim 3 or 4 in which the pad contacting member is provided with flanges which limit its movement towards and away from the associated disc.

6. A caliper according to Claim 5 in which the pad contacting member is secured to the support member by a pin which passes through holes in the flanges and a bore in the support member.

7. A caliper according to any one of claims 4 to 6 in which the resilient means comprises one or more leaf spring elements disposed between the pad contacting member and the support member.

8. A caliper according to any one of claims 1 to 7 in which said at least one abutment includes a layer of low heat conductivity material to reduce heat transfer by conduction from the pad to the caliper body.

9. A caliper according to any one of claims 1 to 8 in which said at least one abutment is formed at an angle to the associated brake disc so that as the pad is moved towards the disc the pad is also displaced circumferentially to a limited extent in the same direction as the normal forward direction of rotation of the associated disc.

10. A disc brake caliper constructed and arranged substantially as hereinbefore described with reference to and as shown in figures 1 to 7 or 8 of the accompanying drawings.